https://practicaltypography.com is a pretty nice introduction on the topic, but overall, if there's any one major thing to keep in mind,
It's this:
Use white space.
The difference between something that looks thrown together and something that looks professional often come down to simply giving a shit about where text is and where text isn't. Does it look good? No? Try again.
Beyond that, don't go crazy with fonts. Two-maybe three weights/variants of one typeface will probably be sufficient -- I've generally found it's a lot easier for an amateur to make things that don't suck when they aren't trying to pair fonts.